Synthesis and reactions of 2-(p-chloroanilino)-5- (D-galacto-1,2,3,4,5-pentahydroxypentyl)-1,3,4-thiadiazole

Oxidative cyclization of D -galactose (p-chlorophenyl)thiosemicarbazone gave 2-(p-chloroanilino)-5-( D -galacto-1,2,3,4,5-pentahydroxypentyl)-1,3,4-thiadiazole ( 1 ), whose acetylation afforded 2-[N-acetyl-N-(p-chlorophenyl)]-amino-5-( D -galacto-1,2,3,4,5-pentacetoxypentyl)- 1,3,4-thiadiazole ( 3 ). Its periodate oxidation of the glycol groups gave 2-(p-chloroanilino)-1,3,4-thiadiazole-5-carboxaldehyde ( 4 ), which can be transformed into 1,2-[2-(p-chloroanilino)-1,3,4-thiadiazol-5-yl]-1-hydroxy-2-oxoethane. A number of hydrazones of the formyl thiadiazole was prepared and its reduction with sodium borohydride gave 2-(p-chloroanilino)-5-hydroxymethyl-1,3,4-thiadiazole ( 6 ), whose acetylation gave a mono-O-acetyl derivative ( 7 ). Oxidation of the formyl thiadiazole gave 2-(p-chloroanilino)-1,3,4-thiadiazole ( 9 ). The spectral data of the compounds were discussed.     

Transition metal nanoparticles doped carbon paper as a cost-effective anode in a microbial fuel cell powered by pure and mixed biocatalyst cultures

The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs.     

Introducing overview articles in Signal Processing Transactions [Society News]

The IEEE Signal Processing Society is introducing a new feature that originated from a suggestion made by my colleague Athina Petropulu and a couple of associate editors. The publication of overview articles in the transactions will be a service to our readers and appeal to the broad signal processing audience.     

AC susceptibility and hyperfine interactions of vanadium substituted barium nanohexaferrites

Vanadium ions substituted BaFe₁₂O₁₉ nanohexaferrites, BaFe_12-xV_xO₁₉ (0.0?≤x?≤?0.1), were produced through the sol-gel auto-combustion route. The structure, morphology and the elemental compositions of various products were examined using X–ray powder diffraction, scanning electron microscopy coupled with EDX and EDS elemental mapping. These techniques confirmed the formation of the desired Ba-nanohexaferrite phases. The crystallites size was found to be 55–58?nm range for all products. The magnetic properties of BaFe_12-xV_xO₁₉ nanohexaferrites were investigated by Mossbauer spectroscopy, ZFC-FC magnetizations and AC susceptibility. The evolutions in the values of hyperfine magnetic field, isomer shift, quadrupole splitting, and line width were deduced via Mossbauer analysis. The experiments of ZFC and FC magnetizations indicated that no blocking temperature is observed in the temperature interval 2–400?K, which signals the typical ferromagnetic (FM) behavior for the produced nanohexaferrites. A super-spin glass like behavior is noticed at lower temperatures. The experiments AC susceptibility confirmed that the strength of magnetic interactions is enhanced for lower content of V³⁺ (x?=?0.02). For higher amount of V³⁺, the magnetic interactions are weakened. The obtained results are mainly accredited to the substitutions of Fe³⁺ ions by V³⁺ ions.     

Electrochemical bleaching of kraft bagasse pulp using a new cell design

In situ single‐stage electrochemical bleaching of kraft bagasse pulp was carried out in a cylindrical agitated vessel fitted with four graphite rod anodes and a cylindrical stainless steel screen cathode, using NaCl as an electrolyte. The effect of current density, pH, NaCl concentration, impeller rotational speed, temperature, and pulp consistency on the rate of bleaching was studied. It was found that the rate of bleaching increased with increasing current density, NaCl concentration, and temperature and decreased with increasing pH and pulp consistency. The effect of temperature was found to fit Arrhenius equation with an activation energy of 0.515 kcal/mol, which denotes a diffusion‐controlled mechanism. Energy consumption (EC) calculation showed that EC ranged from 0.225 to 3.11 kWh/kg dry pulp depending on the current density. The strength of bleached pulp was little affected by bleaching lying within an acceptable range.     

Essais saoudiens sur les ciments importés

Au fur et à mesure que le développement s'accélère en Arabie saoudite, les matériaux importés deviennent de plus en plus nombreux et entrent en concurrence les uns avec les autres. Le Materials Testing Laboratory de Riyad a procédé, il ny a pas très longtemps, à une étude comparative d'échantillons de ciments importés et de ciments fabriqués dans le pays. S'ils concernent avant tout les chimistes du ciment, les résultats n'en présentent pas moins un intérêt plus général.     

Linear estimation in Krein spaces. II. Applications

We have shown that several interesting problems in H^∞ -filtering, quadratic game theory, and risk sensitive control and estimation follow as special cases of the Krein-space linear estimation theory developed in Part I. We show that all these problems can be cast into the problem of calculating the stationary point of certain second-order forms, and that by considering the appropriate state space models and error Gramians, we can use the Krein-space estimation theory to calculate the stationary points and study their properties. The approach discussed here allows for interesting generalizations, such as finite memory adaptive filtering with varying sliding patterns     

Flavonol glycosides and flavonol glucoside gallates from Peltophorum africanum

In this study of interactions occurring within the heart, isolated superfused strips of rabbit atria, containing the sinoatrial (s.a.) node, were subjected to sinusoidal subthreshold current pulses of varied frequencies and intensities. A.C. current from an R.C. oscillator was applied through a Grass stimulation isolation unit, push-pull connection, and non-polarizing (Ag-AgCl-KCl-Tyrode Agar-Agar) electrodes. A Grass polygraph and tachometer were used to record the applied pulses and nodal firing rates; simultaneous magnetic tape recordings were obtained and used for data analysis. Suction electrode recordings and oscilloscope displays were used to determine how the cyclic impulses affected cellular activity. The s.a. nodal rhythm was modified by subthreshold A.C. current applications; when frequencies were low, firing rates of the node were modulated by the A.C. and mean rates were reduced. As frequencies were progressively increased, slow waxings and wanings in heart rate were produced. These periodic fluctuations were not readily correlated with either the A.C. frequency nor the intrinsic nodal rate, but were representative of the difference between the two. As applied current frequency neared the pacemaker's intrinsic rate, a synchronization occurred and the discharges locked in at a specific phase of the applied current alternation. This synchronization maintained during slight further increases in A.C. frequency but above a critical rate this relationship broke down and the waxing and wanings in frequency of pacemaker rate again developed. It was concluded that pacemaker action of the s.a. node is effected by integration of cellular activity through electron coupling.     

Glass formation, optical properties and local atomic arrangement of chalcogenide systems GeTe-Cu and GeTe-In

Glass-forming regions of ternary Ge-Te-Cu and Ge-Te-In chalcogenide glasses are examined by differential scanning calorimeter and by X-ray diffraction. Glass transition and crystallization temperatures are about 120 °C To 260 °C, respectively higher than those of binary Ge-Te glass [T. Katsuyama and M. Matsumura, Infrared Optical Fibres (Adam Hilger, London, 1989) p. 212]. Only a small range of compositions after quenching the melting alloy is characterized by disordered state, but this range of composition is widened when using a vapor deposition technique. These compositions have two glass transition temperatures, showing the existence of phases in the sample. Both the Kissinger equation and modified Kissinger kinetic analysis were adopted to estimate activation energy and the reaction order of the process. Ge-Te-Cu and Ge-Te-In crystallized in two stages, nucleation and crystal growth. These two processes can be distinguished by exothermal crystallization patterns. An atomic radial distribution analysis has been made on bulk Ge₁Te₄In _x and Ge₁Te₄Cu _x with x = 0.1 by X-ray diffraction techniques. The radial distribution function (RDF) is discussed in terms of the structure factor F(s). Thin films of Ge-Te-Cu and Ge-Te-In are deposited on silicate glass and silicon wafer substrates by vacuum evaporation. The optical energy E _opt are determined from transmission and reflection data of a deposited films. The value of E _opt decreased by increasing metal additive such as Cu or In and discussed as a function of the conditions of their preparation such as substrate type.     

Volume Changes of Iron Oxide Compacts under Isothermal Reduction Conditions

Compacts made from chemically grade Fe₂O₃ were fired at 1473K for 6 hrs. The fired compacts were isothermally reduced either by hydrogen or carbon monoxide at 1073–1373K. The O₂ weight‐loss resulting from the reduction process was continuously recorded as a function of time using TGA technique, whereas the volume change at different reduction conditions was measured by displacement method. Porosity measurements, microscopic examination and X‐ray diffraction analysis were used to characterize the fired and reduced products. The rate of reduction at both the initial and final stages was increased with temperature. The reduction mechanism deduced from the correlations between apparent activation energy values, structure of partially reduced compacts and application of gas‐solid reaction models revealed the reduction rate (dr/dt) at both the initial and final stages. At early stages, the reduction was controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism, while at the final stages the interfacial chemical reaction was the rate determining step. In H₂ reduction, maximum swelling (80%) was obtained at 1373K, which was attributed to the formation of metallic iron plates. In CO reduction, catastrophic swelling (255%) was obtained at 1198K due to the formation of metallic iron plates and whiskers.